Electrically conductive polyaniline composition, film thereof and method of producing them

ABSTRACT

The invention provides an electrically conductive polyaniline composition comprising polyaniline which contains at least one of novolac resins selected from the group consisting of phenolsulfonic acid novolac resin and naphtholsulfonic acid novolac resin as a dopant. The electrically conductive polyaniline composition is obtained by contacting polyaniline with an aqueous solution of the novolac resin to dope the polyaniline with the novolac resin. 
     The invention further provides an electrically conductive polyaniline film which comprises the polyaniline containing the novolac resin as a dopant. The electrically conductive polyaniline film is obtained by contacting film of polyaniline with an aqueous solution of the novolac resin to dope the polyaniline.

This is a Ser. No. 10/499,064, filed Jun. 17, 2004, which is a 371 ofPCT/JP02/06450 filed Jun. 26, 2002.

TECHNICAL FIELD

The present invention relates to an electrically conductive polyanilinecomposition superior in water resistance, a film thereof and a method ofproducing them.

BACKGROUND ART

In recent years, electrically conductive polyaniline compositionscomprising polyaniline and dopant have been notable and used in variousfields. For example, it is described in Japanese Unexamined PatentPublication No. 3-35516 that a film comprising the above-mentionedelectrically conductive polyaniline composition is used as a solidelectrolyte film in an aluminum electrolytic capacitor or a tantalumelectrolytic capacitor. That is to say, it is described that anelectrolytic capacitor superior in frequency characteristics can beobtained by applying a polyaniline solution on dielectric film to form apolyaniline film and then by doping the polyaniline film with a protonicacid. In addition, electrically the conductive polyaniline compositionhas been studied for practical use in a multitude of fields such asantistatic materials, electromagnetic shielding materials, magneticrecording media, film capacitors and batteries.

It has been also found out that the polyaniline has an eminently highheat resistance by properly selecting dopants. For example, it isdescribed in Japanese Unexamined Patent Publication No. 10-36667 that anelectrically conductive polyaniline composition containing an aliphaticmonosulfonic acid having a carboxyl group as a dopant exhibits a veryhigh heat resistance and that the decrease of electric conductivity iswithin one tenth of the initial value even after standing at atemperature of 125° C. for 650 hours.

It has, however, been conventionally pointed out that an electricallyconductive polyaniline composition is not necessarily sufficient inwater resistance which is important in practical use together with heatresistance. It has been then proposed that a polymer sulfonic acid isused as a dopant. It has been indeed already known as described inJapanese Unexamined Patent Publication No. 3-28229 that an electricallyconductive polyaniline composition is provided with improved waterresistance by using a polymer sulfonic acid as a dopant compared withthe case of using a low-molecular weight sulfonic acid as a dopant.

When a polymer sulfonic acid such as polyvinylsulfonic acid is used as adopant, it is true that a polyaniline composition obtained is improvedin water resistance as compared with the case of using a low-molecularweight sulfonic acid compound; however, after the polyanilinecomposition is immersed in water for a long period, the decrease ofelectric conductivity of the composition is inevitable to a certaindegree. The degree of the decrease of electric conductivity isapproximately 1/400 of the initial value after being immersed in waterfor 500 hours.

DISCLOSURE OF THE INVENTION

The present invention has been completed to solve the problems mentionedabove in electrically conductive polyaniline compositions. Accordingly,it is an object of the invention to provide an electrically conductivepolyaniline composition superior in water resistance and heatresistance, a film thereof and a method of producing them.

The invention provides an electrically conductive polyanilinecomposition comprising polyaniline doped with at least one novolac resinselected from the group consisting of phenolsulfonic acid novolac resinsand naphtholsulfonic acid novolac resins.

Such an electrically conductive polyaniline composition can be obtainedby contacting polyaniline with an aqueous solution of theabove-mentioned novolac resin to dope the polyaniline with theabove-mentioned novolac resin, in accordance with the present invention.

Also, the invention provides a film comprising an electricallyconductive polyaniline in which polyaniline is doped with theabove-mentioned novolac resin. Such a film comprising electricallyconductive polyaniline can be obtained by contacting a polyaniline filmwith an aqueous solution of the novolac resin to dope the polyanilinewith the novolac resin in accordance with the invention.

Further, according to the invention, an electrically conductivepolyaniline composition comprising polyaniline doped with the novolacresin is obtained by performing chemical oxidation polymerization orelectrolytic oxidation polymerization of aniline in an aqueous solutionin which the above-mentioned novolac resin and aniline are dissolved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the variations with time of electricconductivity of a film of electrically conductive polyaniline comprisingpolyaniline doped with p-phenolsulfonic acid novolac resin in accordancewith the invention when it is immersed in distilled water while beingcompared with that of a film of electrically conductive polyanilinecomprising polyaniline doped with polyvinylsulfonic acid.

FIG. 2 is a graph showing the variations with time of electricconductivity of a film of electrically conductive polyaniline comprisingpolyaniline doped with p-phenolsulfonic acid novolac resin in accordancewith the invention when it is placed under an atmosphere of 125° C.while being compared with that of a film of electrically conductivepolyaniline comprising polyaniline doped with polyvinylsulfonic acid.

BEST MODE FOR CARRYING OUT THE INVENTION

An electrically conductive polyaniline composition according to theinvention comprises polyaniline doped with at least one novolac resinselected from the group consisting of phenolsulfonic acid novolac resinsand naphtholsulfonic acid novolac resins.

According to the invention, the polyaniline preferably comprises arepeating unit represented by the general formula (I)

wherein m and n denote molar fractions of a quinonediimine structuralunit and a phenylenediamine structural unit in the repeating unit,respectively, and satisfy the conditions: 0≦m≦1, 0≦n≦1 and m+n=1. Thepolyaniline is soluble in organic solvents when it is undoped. Accordingto the invention, the polyaniline has an intrinsic viscosity [η]preferably of 0.40 dL/g or more, particularly preferably of 1.0 dL/g ormore, measured at a temperature of 30° C. in N-methyl-2-pyrrolidone.Such polyaniline is hereinafter referred to as “the oxidized and dedopedpolyaniline”.

The oxidized and dedoped polyaniline as mentioned above has been alreadyknown as described in Japanese Unexamined Patent Publication No.3-28229, and can be obtained by first producing an electricallyconductive polyaniline composition doped with a protonic acid and thendedope the composition.

More specifically, aniline is reacted with an oxidizing agent such asammonium peroxodisulfate in the presence of a protonic acid such assulfuric acid in a solvent such as water or methanol, and then thedeposited powder is collected by filtration, thereby providing anelectrically conductive polyaniline composition doped with the protonicacid. Then, the powder is added to an aqueous solution of an alkalinesubstance such as ammonia to neutralize (namely, dedope) theelectrically conductive polyaniline composition, thereby providingpowder of oxidized and dedoped polyaniline soluble in organic solventsrepresented by the above-mentioned general formula (I).

The oxidized and dedoped polyaniline thus obtained has a high molecularweight and is soluble in various organic solvents. More specifically,the polyaniline has an intrinsic viscosity [η] usually of 0.40 dL/g ormore measured at a temperature of 30° C. in N-methyl-2-pyrrolidone, andit is soluble in organic solvents such as N-methyl-2-pyrrolidone,N,N-dimethylacetamide, N,N-dimethyl-formamide, dimethyl sulfoxide,1,3-dimethyl-2-imidazolidinone or sulfolane. The solubility of theoxidized and dedoped polyaniline in such organic solvents depends on theaverage molecular weight thereof and the solvents, but usually 0.5 to100% of the polyaniline can be dissolved to provide a solution having aconcentration of 1 to 30% by weight. In particular, the oxidized anddedoped polyaniline exhibits a high solubility inN-methyl-2-pyrrolidone, and 20 to 100% of the polyaniline can usually bedissolved to provide a solution of 3 to 30% by weight.

Also, the values of m and n of the oxidized and dedoped polyaniline canbe adjusted by oxidizing or reducing the polyaniline. That is, thereduction thereof can decrease the value of m and increase the value ofn, whereas the oxidation thereof can increase the value of m anddecrease the value of n.

In particular, when the quinonediimine structure of the oxidized anddedoped polyaniline is totally reduced, polyaniline comprising animino-p-phenylene structural unit represented by the following formula(II)

is obtained as described in Japanese Unexamined Patent Publication No.3-52929. Such polyaniline is hereinafter referred to as “the reduced anddedoped polyaniline”. The reduced and dedoped polyaniline is soluble infurther diverse organic solvents as compared with the oxidized anddedoped polyaniline. The reduced and dedoped polyaniline is more highlysoluble in solvents such as dimethylformamide, dimethylacetamide ordimethyl sulfoxide as compared with the oxidized and dedopedpolyaniline.

When the oxidized and dedoped polyaniline is reduced, the molecularchain of the polyaniline is not substantially severed, so that thereduced and dedoped polyaniline obtained substantially retains theinitial molecular weight of the oxidized and dedoped polyaniline.Accordingly, the reduced and dedoped polyaniline comprising animino-p-phenylene structural unit represented by the formula (II) alsohas an intrinsic viscosity [η] usually of 0.40 dL/g or more, preferably1.0 dL/g or more, measured at a temperature of 30° C. inN-methyl-2-pyrrolidone.

Reducing agents usable for reducing the oxidized and dedoped polyanilineinclude hydrazine compounds such as phenylhydrazine, hydrazine,hydrazine hydrate, hydrazine sulfate or hydrazine hydrochloride; andhydrogenated reductive metallic compounds such as lithium aluminumhydride or lithium borohydride. Among the exemplified above, hydrazinehydrate or phenylhydrazine is particularly preferred as a reducing agentfor the reason that no residue is generated after the reductionreaction.

In order to reduce the oxidized and dedoped polyaniline using a reducingagent mentioned as above, ant common methods of reduction reaction maybe employed, and they are not particularly limited. Accordingly, theremay be mentioned, for example, a method in which the oxidized anddedoped polyaniline is dissolved in an organic solvent such asN-methyl-2-pyrrolidone, and then the reducing agent is added to thesolution; a method in which the reducing agent is dissolving in organicsolvents such as N-methyl-2-pyrrolidone, dimethylformamide ordimethylacetamide, and then the polyaniline is added to the solution; ora method in which the polyaniline is dispersed in a non-solvent, andthen the reduction reaction is performed in a nonuniform system.

The reduction reaction is performed in a solution containing theoxidized and dedoped polyaniline in an amount usually of 0.1 to 15% byweight, preferably 0.5 to 10% by weight. It is preferred that thereducing agent is usually used in an amount equivalent to the quantityof quinonediimine structures in the oxidized and dedoped polyaniline.However, the reducing agent may be used in an amount more than theequivalent in order to accelerate the progress of the reaction.

In the case of using excessive amount of reducing agent in this manner,however, when the reduced and dedoped polyaniline obtained is directlydoped in a solution, an unpreferable side reaction is occasionallycaused and the decrease of molecular weight by the breakage of polymerchain is caused during a long-term preservation of a solution of thereduced and dedoped polyaniline. Accordingly, in the case of usingexcessive amount of reducing agent, it is desirable that the reduced anddedoped polyaniline obtained is purified by a reprecipitation processand thereafter doped.

On the other hand, oxidizing agents usable for oxidizing oxidized anddedoped polyaniline are not particularly limited if capable of oxidizinga phenylenediamine structural unit. Accordingly, for example, a moderateoxidizing agent, silver oxide, is preferably used. However, potassiumpermanganate, potassium dichromate or the like can be also used ifnecessary.

An electrically conductive polyaniline composition of the inventioncomprises such a polyaniline either oxidized and dedoped or reduced anddedoped with at least one novolac resin selected from the groupconsisting of phenolsulfonic acid novolac resins and naphtholsulfonicacid novolac resins. Such an electrically conductive polyanilinecomposition of the invention is obtained by doping the polyanilineeither oxidized and dedoped or reduced and dedoped with at least onenovolac resin selected from the group consisting of phenolsulfonic acidnovolac resins and naphtholsulfonic acid novolac resins.

An electrically conductive polyaniline composition doped with theabove-mentioned novolac resin according to the invention is alsoobtained by dissolving aniline in an aqueous solution of the novolacresin, and then adding an oxidizing agent to the aqueous solution whilestirred to perform chemical oxidation polymerization of the aniline, orby immersing platinum electrodes in the above-mentioned aqueous solutionand then electrifying with a direct current to perform electrolyticoxidation polymerization of the aniline.

The phenolsulfonic acid novolac resin is preferably represented by thegeneral formula (III)

wherein R₁ denotes a hydrogen atom, an alkyl group, an alkoxyl group, ahydroxyl group, a carboxyl group or an amino group. The phenolsulfonicacid novolac resin is not particularly limited, however,p-phenolsulfonic acid novolac resin in which R₁ is a hydrogen atom andthe substitution position of a sulfonic group is p-position with respectto a hydroxyl group is preferably used among the various phenolsulfonicacid novolac resins represented by the general formula (III).

The naphtholsulfonic acid novolac resin is preferably represented by thegeneral formula (IV)

wherein R₂ and R₃ denote each independently a hydrogen atom, an alkylgroup, an alkoxyl group, a hydroxyl group, a carboxyl group or an aminogroup, and p and q are each independently an integer of 0, 1 or 2,provided that p and q are not simultaneously 0. The naphtholsulfonicacid novolac resin is not particularly limited; however, novolac resinof 1-naphtholsulfonic acid such as 1-naphthol-4-sulfonic acid,1-naphthol-5-sulfonic acid or 1-naphthol-8-sulfonic acid, and 1-naphtholdisulfonic acid such as 1-naphthol-3,6-disulfonic acid or1-naphthol-3,8-disulfonic acid is preferably used among thenaphtholsulfonic acid novolac resins represented by the general formula(IV).

These phenolsulfonic acid novolac resins and naphtholsulfonic acidnovolac resins are not particularly limited with regard to theirmolecular weight; however, it is preferred that they have aweight-average molecular weight in the range of 2000 to 800000 measuredby GPC while using polystyrene sodium sulfonate as a standard polymer.When the molecular weight of phenolsulfonic acid novolac resin ornaphtholsulfonic acid novolac resin is less than 2000, the obtainedelectrically conductive polyaniline composition is not sufficientlyimproved in water resistance. Meanwhile, when the molecular weight ofphenolsulfonic acid novolac resin or naphtholsulfonic acid novolac resinis more than 800000, an aqueous solution of phenolsulfonic acid novolacresin or naphtholsulfonic acid novolac resin used for doping is too highin viscosity to dope polyaniline easily as described later.

First, the production of electrically conductive polyaniline by dopingthe oxidized and dedoped polyaniline with phenolsulfonic acid novolacresin or naphtholsulfonic acid novolac resin is described.

According to the invention, the oxidized and dedoped polyaniline iscontacted with the novolac resin for doping the polyaniline with thenovolac resin. For example, powder of the polyaniline is immersed in anaqueous solution of the novolac resin at room temperature or underheating if necessary. In this case, an aqueous solution may be usedcontaining novolac resin such that the number of moles of sulfonicgroups in the novolac resin is in large excess with respect to thenumber of moles of aniline units in the polyaniline. The doping ofpolyaniline with the novolac resin by contacting polyaniline with thenovolac resin in this manner (in the absence of an oxidizing agent) isreferred to as “protonic acid doping” in the present specification.

It is thought that the protonic acid doping of oxidized and dedopedpolyaniline is caused as illustrated below for the reason that an iminenitrogen atom in polyaniline is protonated by protonic acid so as toproduce an iminium salt. The canonical structure of the iminium salt hasa semiquinone cationic radical structure, which is called a doped stateallowing electrical conductivity to polyaniline.

As described above, the oxidized and dedoped polyaniline used in theinvention is soluble in organic solvents; therefore, it is preferredthat the oxidized and dedoped polyaniline is dissolved in an organicsolvent, cast on a base material, heated and dried, for example, at atemperature of 50 to 150° C. to provide a self-supporting film, and thisfilm is contacted with an aqueous solution of the novolac resin to dopethe polyaniline. A film comprising an electrically conductivepolyaniline composition of the invention, namely, an electricallyconductive polyaniline film can be obtained efficiently and easily inthis manner.

For further details, an electrically conductive polyaniline film isobtained by immersing the self-supporting polyaniline film in an aqueoussolution of the dopant or by applying the aqueous solution of thenovolac resin on the film, and washing the film with an appropriatesolvent if necessary.

The concentration of the aqueous solution of phenolsulfonic acid novolacresin or naphtholsulfonic acid novolac resin used for doping thepolyaniline is not particularly limited, but it is usually in the rangeof 2 to 50% by weight. When the concentration of the aqueous solution ofnovolac resin is less than 2% by weight, a long time is required fordoping. Meanwhile, when the concentration thereof is more than 50% byweight, an aqueous solution of novolac resin is too high in viscosity todope polyaniline easily.

As described above, aniline is reacted with an oxidizing agent in thepresence of protonic acid in a solvent and the deposited powder iscollected by filtration to obtain an electrically conductive polyanilinecomposition doped with the protonic acid. Accordingly, aniline isreacted in a solvent with an oxidizing agent in the presence of eitherphenolsulfonic acid novolac resin or naphtholsulfonic acid novolacresin, and the deposited powder is collected by filtration to provide anelectrically conductive polyaniline composition comprising polyanilinehaving the novolac resins as a dopant. Further, electrolytic oxidationpolymerization of aniline is performed in the presence of phenolsulfonicacid novolac resin or naphtholsulfonic acid novolac resin in a solventto provide an electrically conductive polyaniline composition in whichpolyaniline is doped with the novolac resins.

As oxidizing agents for chemical oxidation polymerization of aniline,those having a standard electrode potential of 0.6 V or more arepreferably used, for example, as described in Japanese Patent No.2649670. Such oxidizing agents include manganese dioxide, potassiumpermanganate, potassium dichromate, hydrogen peroxide or ferricchloride. Ammonium peroxodisulfate is also preferably used. Theseoxidizing agents are used in an amount of equivalent weight of 2 to 2.5in relation to 1 mol of aniline. The equivalent is such an amount thatis obtained by dividing 1 mol (molecular weight=M (g)) of the oxidizingagent by the number of electrons (n) required for reducing one moleculeof the oxidizing agent. Namely, the equivalent is defined as M/n.

In chemical oxidation polymerization of aniline, solvents used are notparticularly limited if they dissolve phenolsulfonic acid novolac resinor naphtholsulfonic acid novolac resin used together with aniline andadditionally are inactive to the reaction; for example, water isparticularly preferably used as described in Japanese Unexamined PatentPublication No. 3-28229. Also, lower aliphatic alcohols such as methanolor ethanol, nitriles such as acetonitrile, polar solvents such asN-methyl-2-pyrrolidone or dimethyl sulfoxide, or tetrahydrofuran areused. Further, mixed solvents of these organic solvents and water areused. On the other hand, phenolsulfonic acid novolac resin ornaphtholsulfonic acid novolac resin as a protonic acid is usually usedin large excess with respect to aniline.

Chemical oxidation polymerization of aniline is preferably performed ata temperature of 10° C. or less. In order to obtain high-molecularweight polyaniline, particularly, a reaction mixture is preferablyretained at a temperature of 10° C. or less on the occasion of adding anoxidizing agent to an aniline solution containing phenolsulfonic acidnovolac resin or naphtholsulfonic acid novolac resin.

An electrically conductive polyaniline composition comprisingpolyaniline doped with phenolsulfonic acid novolac resin ornaphtholsulfonic acid novolac resin, namely, an electrically conductivepolyaniline composition having the novolac resins as a dopant isprecipitated as powder when such chemical oxidation polymerization ofaniline is carried out. Thus, the powder is collected by filtration anddried whereby an electrically conductive polyaniline composition of theinvention is obtained.

In the case of performing electrolytic oxidation polymerization ofaniline, an electrically conductive polyaniline composition of theinvention is obtained by immersing a pair of platinum electrodes in asolution as mentioned above that contains aniline as well as eitherphenolsulfonic acid novolac resin or naphtholsulfonic acid novolac resinin an amount equal or more to the aniline in terms of moles of thesulfonic groups of the resin, and then performing constant-potentialpolymerization through the application of an electric potential of 0.6to 1.2 V with respect to the standard calomel electrodes connected by asalt bridge, or performing constant-current polymerization under theconditions of a current density of 0.1 to 50 mA/cm², or employing anelectric potential scanning process of performing electrolyticpolymerization through the scanning of an electric potential in a rangeof 0 to 0.8 V with respect to the standard calomel electrodes.

The production of electrically conductive polyaniline by doping thereduced and dedoped polyaniline with either phenolsulfonic acid novolacresin or naphtholsulfonic acid novolac resin is now described.

According to the invention, the reduced and dedoped polyaniline ispreferably reacted with the novolac resin in the presence of anoxidizing agent in order to dope the polyaniline with the phenolsulfonicacid novolac resin or naphtholsulfonic acid novolac resin. Also, thereduced and dedoped polyaniline may be doped by reacting the polyanilinewith the novolac resin while oxidizing with the use of electrodes forelectrolysis instead of an oxidizing agent.

The doping of the polyaniline with the phenolsulfonic acid novolac resinor the naphtholsulfonic acid novolac resin while oxidizing thepolyaniline in this manner is referred to as “oxidation doping” in thepresent specification. According to the invention, the reduced anddedoped polyaniline is doped very promptly by performing such oxidationdoping, whereby an electrically conductive polyaniline compositionhaving the novolac resin as a dopant is readily obtained.

According to the invention, the phenolsulfonic acid novolac resin andthe naphtholsulfonic acid novolac resin used in the oxidation doping ofthe reduced and dedoped polyaniline each may be in the form of alkalimetal salts, ammonium salts or organic amine salts. The alkali metalsalts include, for example, sodium salt and potassium salt, and theorganic amine salts include triethylamine salt, ethanolamine salt orethylenediamine salt, however, they are not limited thereto.

In such oxidation doping, it is thought that the polyaniline is oxidizedand then one of unshared electron pairs on a nitrogen atom thereof istaken away so as to cause a positive charge on the nitrogen atom andsubsequently protonic acid anion existing in the reaction systemapproaches this positive charge so as to cancel out the above-mentionedpositive charge and thus retain charge neutrality, whereby theabove-mentioned nitrogen atom of polyaniline is made into a cationicradical. In this manner, polyaniline has the same semiquinone cationicradical structure as described above to have electrical conductivity.

Oxidizing agents used for the oxidation doping are not particularlylimited if capable of oxidizing the reduced and dedoped polyaniline; forexample, including ferric salts such as ferric chloride, ferricperchlorate or ferric oxalate, cupric salts such as cupric chloride orcupric perchlorate, cuprous chloride (air oxidation catalyst),persulfates such as ammonium persulfate, dichromates such as potassiumdichromate, permanganates such as potassium permanganate, iodates suchas sodium iodate, chlorates such as sodium chlorate, hydrogen peroxide,manganese dioxide, ammonium cerium nitrate, lead oxide, quinone-basedoxidizing agents, and the like. Specific examples of the quinone-basedoxidizing agents include p-benzoquinone, o-benzoquinone, p-toluquinone,1,2-naphthoquinone, 1,4-naphthoquinone, diphenoquinone, chloranil,2,3-dichloro-5,6-dicyano-p-benzoquinone, tetracyanoquinodimethane,sodium 1,2-naphthoquinone-4-sulfonate, sodium1,4-naphthoquinone-2-sulfonate, tetrafluoro-p-benzoquinone, and thelike.

On the occasion of oxidation doping of reduced and dedoped polyaniline,it is not necessary to oxidize the total imino-p-phenylene structuralunits of polyaniline; therefore, the amount of the oxidizing agent usedis not particularly limited, however, the oxidizing agent is usuallyused in the range of 1/10 of equivalent weight to a large excess withrespect to the imino-p-phenylene structural units of polyaniline. Theoxidizing agent is usually used as a solution having a concentration of0.1 to 30% by weight, preferably an aqueous solution. The reasontherefore is that an excessively low concentration of the oxidizingagent wastefully requires a long time for oxidation doping ofpolyaniline, while an excessively high concentration of the oxidizingagent causes the breakage of the molecular chain of polyaniline on theoccasion of oxidation doping of polyaniline so as to bring thedeterioration of polyaniline such as the decrease of the molecularweight of polyaniline.

The concentration of an aqueous solution of phenolsulfonic acid novolacresin or naphtholsulfonic acid novolac resin used for doping the reducedand dedoped polyaniline is not particularly limited; usually, in therange of 2 to 50% by weight as described above.

The doping of the reduced and dedoped polyaniline may be performed atroom temperature, however, the doping under heating at a temperature of50 to 100° C. reduces the time required for the doping as compared withthe doping at room temperature.

The time required for doping is determined by measuring the electricconductivity of polyaniline obtained; usually, in the range ofapproximately 10 minutes to 10 hours. In the case of doping by addingpowder of reduced and dedoped polyaniline to an aqueous solution ofphenolsulfonic acid novolac resin or naphtholsulfonic acid novolacresin, the powder is pale blue at first and rendered dark green bydoping.

The reduced and the dedoped polyaniline also is soluble in organicsolvents similarly to the oxidized and dedoped polyaniline; therefore,the reduced and the dedoped polyaniline is dissolved in an organicsolvent, cast on a base material, and heated and dried, for example, ata temperature of 50 to 150° C. to provide a self-supporting film, andthen the film is subjected to oxidation doping, thereby providing a filmcomprising electrically conductive polyaniline. For example, an aqueoussolution containing phenolsulfonic acid novolac resin ornaphtholsulfonic acid novolac resin with an oxidizing agent is preparedas a doping treatment solution, and then the polyaniline film isimmersed in the doping treatment solution, or the doping treatmentsolution is applied on the film, and then the film is washed with asolvent if necessary, thereby providing an electrically conductivepolyaniline film of the invention.

When the oxidation doping is performed for a film comprising the reducedand dedoped polyaniline in this manner, the color of the film is paleblue at first, and it changes to dark blue after doping. In accordancetherewith, the electric conductivity of the film is approximately 10⁻¹⁰S/cm before doping and then as high as 10⁰ to 10² S/cm after doping.

An electrically conductive polyaniline composition thus obtainedcontains sulfonic ions derived from phenolsulfonic acid novolac resin ornaphtholsulfonic acid novolac resin as a dopant in an amount usually of15 to 75% of the number of moles of aniline units in polyaniline.According to the invention, in an electrically conductive polyanilinecomposition, 15 to 75% of the total nitrogen atoms in the polyanilineare converted into cationic radicals, to which nitrogen atoms an equalnumber of anions (sulfonic ions) derived from the dopant have ionicbonds. When 50 mol % of aniline units in polymer are thus doped, theelectric conductivity of polyaniline is rendered the highest.

The electrically conductive polyaniline composition and a film thereofaccording to the invention exhibit a remarkably high water resistance.An electrically conductive polyaniline composition comprisingpolyaniline doped with polyvinylsulfonic acid has been conventionallyknown for having a comparatively high water resistance; nevertheless,when it is immersed in distilled water for 500 hours, the electricconductivity thereof reduces to approximately 1/400 of the initialvalue. On the contrary, with regard to an electrically conductivepolyaniline composition comprising polyaniline doped with phenolsulfonicacid novolac resin or naphtholsulfonic acid novolac resin in accordancewith the invention, the decrease of the electric conductivity thereof iswithin 1/10 of the initial value even if immersed in distilled water for500 hours.

The reason why the electrically conductive polyaniline composition and afilm thereof of the invention have such a high water resistance is notnecessarily evident, and the invention has no restrictions by theory; itis thought that the reason is that phenolic hydroxyl groups in thephenolsulfonic acid novolac resin or the naphtholsulfonic acid novolacresin intensify the interaction with polyaniline to resultingly controlthe desorption of the novolac resin as a dopant from polyaniline,namely, dedoping.

In addition, the electrically conductive polyaniline composition and afilm thereof of the invention are superior in heat resistance and haveapproximately equal heat resistance to an electrically conductivepolyaniline composition having polyvinylsulfonic acid as a dopant and afilm thereof, which have been conventionally known for having acomparatively high heat resistance.

INDUSTRIAL APPLICABILITY

As described above, the electrically conductive polyaniline compositionobtained by doping polyaniline with phenolsulfonic acid novolac resin ornaphtholsulfonic acid novolac resin and a film thereof in accordancewith the invention have superior water resistance and heat resistance,and can be appropriately used as electrically conductive polymericmaterials in various fields. In particular, an electrically conductivepolyaniline composition according to the invention can be appropriatelyused, for example, as cathode materials in an aluminum electrolyticcapacitor and a tantalum electrolytic capacitor, and additionally can beappropriately used as materials having water resistance and heatresistance in various uses such as antistatic materials, electrodes fororganic electroluminescence, electromagnetic shielding materials andanti-corrosive materials.

EXAMPLES

The invention is described below by referring to examples together withreference examples, but the invention is not limited thereto.

Reference Example 1

The Production of an Electrically Conductive Polyaniline Composition byOxidation Polymerization of Aniline

6000 g of distilled water, 360 mL of 36%-hydrochloric acid and 400 g(4.295 mol) of aniline were charged in this order into a 10 L-capacityseparable flask provided with a stirring apparatus, a thermometer and astraight tube adapter and the aniline was dissolved in the aqueoussolution of hydrochloric acid. 434 g (4.295 mol) of 97%-concentratedsulfuric acid was added to and mixed with 1493 g of distilled water in abeaker while cooled by iced water to prepare an aqueous solution ofsulfuric acid. The aqueous solution of sulfuric acid was added to theabove-mentioned separable flask and the total flask was cooled to atemperature of −4° C. in a low-temperature controlled bath. Then, 980 g(4.295 mol) of ammonium peroxodisulfate was added to and dissolved in2293 g of distilled water in a beaker to prepare an aqueous solution ofan oxidizing agent.

While stirring and retaining the temperature of the acidic aqueoussolution of aniline salt at −3° C. or less by cooling the total flask inthe low-temperature controlled bath, the aqueous solution of ammoniumperoxodisulfate was gradually dropped thereto from the straight tubeadapter at a rate of 1 mL/minute or less by using a tubing pump. Thesolution was at first colorless and transparent, and then it changed incolor from greenish blue to dark green as the polymerization progresses,and subsequently powder in dark green was deposited.

A rise in temperature was observed in the reaction mixture during thedeposition of powder, and also in this case, it is important to controlthe temperature in a reaction system at 0° C. or less, preferably −3° C.or less in order to obtain high-molecular weight polyaniline inaccordance with the invention. The dropping rate of the aqueous solutionof ammonium peroxodisulfate may be rendered somewhat higher, such as 8mL/minute, after the deposition of powder, also in which case, however,it is required to adjust the dropping rate so as to retain thetemperature at −3° C. or less while monitoring the temperature of thereaction mixture. Thus, after finishing the dropping of the aqueoussolution of ammonium peroxodisulfate in 7 hours, the stirring wasfurther continued at a temperature of −3° C. or less for 1 hour.

The obtained powder was collected by filtration, washed with water andacetone, and vacuum-dried at room temperature to provide 430 g of powderof an electrically conductive polyaniline composition in dark green. Thepowder was pressure-molded into a disk having a diameter of 13 mm and athickness of 700 μm. The disk was found to have an electric conductivityof 14 S/cm measured by Van der Pauw method.

(The Production of Oxidized and Dedoped Polyaniline Soluble in OrganicSolvents by Dedoping the Electrically Conductive PolyanilineComposition)

350 g of powder of the above-mentioned doped and electrically conductivepolyaniline composition was added to 4 L of 2N-ammonia water and stirredat a rate of 5000 rpm by an autohomomixer for 5 hours. The mixturechanged in color from dark green to bluish purple.

The powder was collected by filtration with a Buchner funnel andrepeatedly washed with distilled water while stirred in a beaker untilthe filtrate became neutral, and subsequently washed with acetone untilthe filtrate became colorless. Thereafter, the powder was vacuum-driedat room temperature for 10 hours to provide 280 g of powder of oxidizedand dedoped polyaniline in dark brown.

The oxidized and dedoped polyaniline thus obtained was soluble inN-methyl-2-pyrrolidone and the solubility thereof was 8 g (7.4%) in 100g of the solvent. The intrinsic viscosity [η] measured at a temperatureof 30° C. using N-methyl-2-pyrrolidone as a solvent was 1.23 dL/g. Thispolyaniline had a solubility of 1% or less in dimethyl sulfoxide and indimethylformamide, and was substantially insoluble in any oftetrahydrofuran, pyridine, 80%-aqueous solution of acetic acid,60%-aqueous solution of formic acid and acetonitrile.

Further, the oxidized and dedoped polyaniline was found to have anumber-average molecular weight of 23000 and a weight-average molecularweight of 160000 (both were calculated in terms of polystyrene) as aresult of GPC measurement by using a GPC column forN-methyl-2-pyrrolidone.

Reference Example 2

(The Production of Reduced and Dedoped Polyaniline)

2.5 g of powder of the oxidized and dedoped polyaniline obtained inReference Example 1 was added to 97.5 g of N-methyl-2-pyrrolidone anddissolved therein while stirred, and 0.82 g of phenylhydrazine wasgradually added to this solution. Then, the solution changed in colorfrom deep blue to light dark brown, and concurrently the generation ofnitrogen gas was confirmed.

After the reaction, the reaction mixture was dropped into 1.5 L ofacetone substituted with nitrogen to provide precipitate in light gray.The precipitate was collected by filtration with a glass filter andwashed with acetone substituted with nitrogen several times andthereafter dried under reduced pressure at room temperature to provide2.3 g of reduced and dedoped aniline comprising an imino-p-phenylenestructural unit as powder in light gray. The polyaniline thus obtainedwas found to have an intrinsic viscosity [η] of 1.1 dL/g measured inN-methyl-2-pyrrolidone at a temperature of 30° C.

Example 1

10 g of powder of the oxidized and dedoped polyaniline obtained inReference Example 1 was dissolved in 90 g of N-methyl-2-pyrrolidone toprepare a 10% by weight-solution. Four sheets of pressure-sensitiveadhesive tapes having a thickness of 120 μm were stuck in piles on bothends of an A4-size glass plate so as to form a bank, and the solution ofpolyaniline in N-methyl-2-pyrrolidone was cast thereon, drawn through aglass rod and thereafter dried at a temperature of 80° C. for 1 hour ina hot-air circulating type drier. The polyaniline film thus obtained waspeeled off the glass plate. The thickness of the polyaniline film thusobtained was 42 μm. Three sheets of 1 cm-square films were cut out ofthis film.

An aqueous solution of p-phenolsulfonic acid novolac resin (availablefrom Konishi Chemical Industry Co., Ltd., and having a weight-averagemolecular weight of 20000 calculated in terms of sodium polystyrenesulfonate as a result of GPC measurement) was prepared at a solidsconcentration of 20% by weight and 30 g of the solution was placed in aglass sample tube of 50-mL capacity. The glass sample tube was thenimmersed in a 80° C.-temperature controlled bath. After immersion for 30minutes, three sheets of the above-mentioned polyaniline films wereimmersed in the aqueous solution of phenolsulfonic acid novolac resin inthe sample tube for 1 hour so that they were doped.

After the doping treatment, the polyaniline films were taken out andeach washed with 30 mL of methanol three times to remove the novolacresin adhering to the surfaces of the films, and then dried in a drierat a temperature of 80° C. for 30 minutes, thereby providing threesheets of films comprising an electrically conductive polyanilinecomposition having p-phenolsulfonic acid novolac resin as a dopant.These three sheets of films were found to have electric conductivitiesof 8.8 S/cm, 9.5 S/cm and 10.35 S/cm, respectively, measured by Van derPauw method.

Among these three sheets of films, the one having an electricconductivity of 10.35 S/cm was subjected to elemental analysis by flaskcombustion method/ion chromatograph to measure the content of sulfur anddoping efficiency was calculated based thereon to show that the dopingefficiency of polyaniline was 30%. That is, it was confirmed that 30% ofaniline units of polyaniline (namely, nitrogen atoms in polyaniline)were doped with sulfonic ions of p-phenolsulfonic acid novolac resin.

Further, among the above-mentioned three sheets of films, the one havingan electric conductivity of 8.8 S/cm was immersed in 15 mL of distilledwater in a glass sample tube of 20-mL capacity and then taken out withtime so as to measure the electric conductivity thereof. The results areshown in FIG. 1. As clarified in FIG. 1, it is denoted that theelectrically conductive polyaniline film of the invention has anelectric conductivity of 1.3 S/cm even after being immersed in distilledwater for 578 hours. Accordingly, it has a high water resistance as thedecrease of the electric conductivity after the immersion in distilledwater is within 1/10 of the initial electric conductivity.

The film having an electric conductivity of 9.5 S/cm was stuck crosswiseon a 10 cm-square glass plate with a 2-mm-wide pressure-sensitiveadhesive tape made of polytetrafluorethylene resin, placed in a hot-aircirculating type drier at a temperature of 125° C. and then taken outwith time so as to measure the electric conductivity thereof. Theresults are shown in FIG. 2. As clarified in FIG. 2, it is denoted thatthe electrically conductive polyaniline film of the invention has asuperior heat resistance.

Comparative Example 1

An aqueous solution of sodium polyvinylsulfonate available from AldrichCorporation was ion-exchanged by strongly acidic cation-exchange resinDowex W-50×12 (available from The Dow Chemical Company) to prepare a 20%by weight-aqueous solution of free acid type polyvinylsulfonic acid.

The same manner as Example 1 was performed except for using thepolyvinylsulfonic acid as mentioned above as a dopant to provide twosheets of electrically conductive polyaniline films having thepolyvinylsulfonic acid as a dopant, whose electric conductivities were3.7 S/cm and 7.1 S/cm, respectively.

Among these two sheets of films, the one having an electric conductivityof 3.7 S/cm was subjected to water resistance test in the same manner asExample 1. As the results are shown in FIG. 2, the film was found tohave an electric conductivity of 9.2×10⁻³ S/cm, that is, 1/400 of theinitial electric conductivity when immersed in distilled water for 554hours. Also, heat resistance test was performed for the film having anelectric conductivity of 7.1 S/cm in the same manner as Example 1. Theresults are shown in FIG. 2.

Example 2

An aqueous solution of phenolsulfonic acid novolac resin (available fromKonishi Chemical Industry Co., Ltd., and having a weight-averagemolecular weight of 20000 calculated in terms of sodium polystyrenesulfonate as a result of GPC measurement) was prepared at a solidsconcentration of 20% by weight and 180 mL of the solution was placed ina 300 mL-capacity separable flask provided with a stirring apparatus, athermometer and a straight tube adapter. 12.0 g of aniline was furtheradded to and dissolved in the solution while stirred, and the totalseparable flask was cooled to a temperature of −5° C. by using alow-temperature controlled bath.

Then, 28.4 g of ammonium peroxodisulfate was dissolved in 66.3 g ofion-exchange water to prepare a colorless and transparent aqueoussolution. The aqueous solution of ammonium peroxodisulfate was graduallydropped from the straight tube adapter to the aqueous solution ofaniline containing the phenolsulfonic acid novolac resin while stirredat a rate of 1 mL/minute or less by using a tubing pump.

The solution was at first colorless and transparent and then changedfrom greenish blue to dark green during the dropping of the aqueoussolution of ammonium peroxodisulfate as the polymerization of anilineprogresses, and subsequently powder in dark green was deposited. As arise in temperature due to heat of reaction was observed in the reactionmixture during this deposition of powder, the temperature of thereaction mixture was controlled at −3° C. or less. Thus, after finishingthe dropping of the aqueous solution of ammonium peroxodisulfate in 45minutes, the stirring was further continued for 30 minutes whileretaining the temperature of the reaction mixture at −3° C. or less.

The obtained powder of polyaniline was collected by filtration, washedwith water and acetone, and then vacuum-dried at room temperature toprovide 16.3 g of powder of an electrically conductive polyanilinecomposition in dark green having phenolsulfonic acid novolac resin as adopant. The powder was molded into a disk having a diameter of 13 mm anda thickness of 740 μm. The disk was found to have an electricconductivity of 9.3 S/cm as a result of measurement by Van der Pauwmethod.

1 g of the powder of the electrically conductive polyaniline compositionwas added to distilled water and was stood at room temperature for 2weeks, and then was collected by filtration, washed with acetone andvacuum-dried at room temperature. The powder was molded into a diskhaving a diameter of 13 mm and a thickness of 765 μm in the same manneras above. The disk was found to have an electric conductivity of 7.6S/cm by measurement by Van der Pauw method. Accordingly, it is denotedthat the electrically conductive polyaniline composition of theinvention has a high water resistance as the decrease of the electricconductivity due to the immersion in distilled water for 2 weeks is veryslight.

Comparative Example 2

The same manner as Example 2 was performed except for replacingphenolsulfonic acid novolac resin with methansulfonic acid in Example 2to provide powder of an electrically conductive polyaniline compositionin dark green having methansulfonic acid as a dopant. The electricconductivity of this electrically conductive polyaniline composition was18.7 S/cm.

In the same manner as Example 2, the powder of the electricallyconductive polyaniline composition was immersed in distilled water in 2weeks and taken out thereof. The electric conductivity of theelectrically conductive polyaniline composition was then measured andwas found to be 2.2×10⁻⁵ S/cm. Thus, it is denoted that the electricconductivity was remarkably reduced after the immersion in distilledwater for 2 weeks.

Example 3

The same manner as Example 1 was performed except for replacing anaqueous solution of p-phenolsulfonic acid novolac resin with an aqueoussolution of 1-naphthol-4-sulfonic acid novolac resin (available fromKonishi Chemical Industry Co., Ltd., and having a weight-averagemolecular weight of 30000 calculated in terms of polystyrene sodiumsulfonate as a result of GPC measurement) in Example 1 to provide threesheets of films comprising an electrically conductive polyanilinecomposition having 1-naphthol-4-sulfonic acid novolac resin as a dopant.These three sheets of films were fount to have electric conductivitiesof 5.5 S/cm, 3.4 S/cm and 6.3 S/cm, respectively, as a result ofmeasurement by Van der Pauw method

Among the three sheets of films, the ones having electric conductivitiesof 5.5 S/cm and 3.4 S/cm, respectively, were subjected to waterresistance test. That is, the two sheets of films were immersed in 15 mLof distilled water in a glass sample tube of 20-mL capacity and stoodunder room temperature for 535 hours, and thereafter were washed withwater and dried to measure the electric conductivity. As a result, thetwo sheets of films were found to have electric conductivities of 3.1S/cm and 1.8 S/cm, respectively. Thus, little change was observed ascompared with the values before being immersed in distilled water.

The film having an electric conductivity of 6.3 S/cm was subjected toheat resistance test. That is, it was stuck crosswise on a 10 cm-squareglass plate with a 2 mm-wide pressure-sensitive adhesive tape made ofpolytetrafluorethylene resin, placed in a hot-air circulating type drierat a temperature of 125° C. After 512 hours, the film was taken out ofthe dryer and was found to have an electric conductivity of 1.3 S/cm;therefore it is denoted to have a superior heat resistance.

Example 4

10 g of powder of the reduced and dedoped polyaniline obtained inReference Example 2 was dissolved in 90 g of N-methyl-2-pyrrolidone toprepare a 10% by weight-solution. Four sheets of pressure-sensitiveadhesive tapes made of polytetrafluorethylene resin having a thicknessof 120 μm were stuck in piles on both ends of an A4-size glass plate soas to form a bank, and the solution of polyaniline inN-methyl-2-pyrrolidone was cast thereon, drawn through a glass rod andthereafter put into a hot-air circulating type drier and dried at atemperature of 80° C. for 1 hour. The polyaniline film thus obtained waspeeled off the glass plate. The thickness of the polyaniline film thusobtained was 38 μm. Four sheets of 1 cm-square films were cut out ofthis film.

An aqueous solution of p-phenolsulfonic acid novolac resin (availablefrom Konishi Chemical Industry Co., Ltd., and having a weight-averagemolecular weight of 20000 calculated in terms of sodium polystyrenesulfonate as a result of GPC measurement) was concentrated with anevaporator until a syrup was obtained. Ethanol was added to the syrup toprepare a solution having a solids concentration of 20% by weight.p-Benzoquinone was added to and dissolve in the solution to prepare asolution of 2.5% by weight in terms of benzoquinone, thereby providing atreatment solution for oxidation doping.

30 g of the treatment solution for doping was put into a glass sampletube of 50-mL capacity, and the above-mentioned four sheets of films ofthe reduced and dedoped polyaniline were immersed in the solution andstood at room temperature. Every two sheets of the polyaniline filmswere taken out thereof in 30 minutes and 1 hour, respectively, andwashed with 30 mL of methanol three times for removing phenolsulfonicacid novolac resin and p-benzoquinone as the oxidizing agent adhering tothe surfaces of the films, followed by drying in a drier at atemperature of 80° C. for 30 minutes.

The electric conductivity of each of the films thus obtained wasmeasured by Van der Pauw method. The electric conductivities of twosheets of polyaniline films A and B doped for 30 minutes were 4.2 S/cmand 5.3 S/cm, respectively, while the electric conductivities of twosheets of polyaniline films C and D doped for 1 hour were 8.9 S/cm and10.1 S/cm, respectively. Then, the films A and C were as were subjectedto water resistance test. That is, they were immersed in 15 mL ofdistilled water in a glass sample tube of 20-mL capacity for 542 hoursand then taken out thereof so as to measure the electric conductivitiesthereof. The electric conductivity of the film A that had been doped for30 minutes was 2.1 S/cm, while the electric conductivity of the film Cthat had been doped for 1 hour was 8.2 S/cm.

The films B and D were subjected to heat resistance test. The films werestuck crosswise on a 10 cm-square glass plate with a 2-mm-widepressure-sensitive adhesive tape made of polytetrafluorethylene resin,put into a hot-air circulating type drier at a temperature of 125° C.over 542 hours and thereafter taken out so as to measure the electricconductivities thereof. The electric conductivity of the film B that hadbeen doped for 30 minutes was 1.1 S/cm, while the electric conductivityof the film D that had been doped for 1 hour was 5.8 S/cm.

After the water resistance test and the heat resistance test, any of thefilms were found to have electric conductivities that had little changeas compared with the initial electric conductivities. Therefore, it isdenoted that the electrically conductive polyaniline film of theinvention has high water resistance and heat resistance.

Comparative Example 3

An aqueous solution of sodium polyvinylsulfonate available from AldrichCorporation was ion-exchanged by strongly acidic cation-exchange resinDowex W-50X12 (available from The Dow Chemical Company to prepare a 20%by weight-aqueous solution of free acid type polyvinylsulfonic acid.

The same manner as Example 4 was performed except for using this aqueoussolution of polyvinylsulfonic acid as a dopant solution to prepare foursheets of electrically conductive polyaniline films having thepolyvinylsulfonic acid as a dopant. The electric conductivities of twosheets of polyaniline films A and B doped for 30 minutes were 18.8 S/cmand 15.3 S/cm, respectively, while the electric conductivities of twosheets of polyaniline films C and D doped for 1 hour were 26.7 S/cm and30.3 S/cm, respectively.

The films A and C were subjected to water resistance test. That is, theywere immersed in 15 mL of distilled water in a glass sample tube of20-mL capacity for 542 hours and thereafter taken out so as to measurethe electric conductivities thereof. The electric conductivity of thefilm A that had been doped for 30 minutes was 4.4×10⁻² S/cm, while theelectric conductivity of the film C that had been doped for 1 hour was7.1×10⁻² S/cm. Accordingly, the electric conductivities of the filmsafter the water resistance test were approximately 1/400 of the initialelectric conductivities.

In turn, the films B and D were subjected to heat resistance test. Thatis, they were stuck crosswise on a 10 cm-square glass plate with a2-mm-wide pressure-sensitive adhesive tape made ofpolytetrafluorethylene resin, put into a hot-air circulating type drierat a temperature of 125° C. over 542 hours and thereafter taken out soas to measure the electric conductivities thereof. The electricconductivity of the film B that had been doped for 30 minutes was 1.2S/cm, while the electric conductivity of the film D that had been dopedfor 1 hour was 3.3 S/cm. Accordingly, the electric conductivities of thefilms after the heat resistance test were approximately 1/10 of theinitial electric conductivities.

Example 5

The same manner as Example 4 was performed except for replacing anaqueous solution of phenolsulfonic acid novolac resin with an aqueoussolution of 1-naphthol-4-sulfonic acid novolac resin (available fromKonishi Chemical Industry Co., Ltd., and having a weight-averagemolecular weight of 30000 calculated in terms of sodium polystyrenesulfonate as a result of GPC measurement) and replacing p-benzoquinoneas the oxidizing agent with 2,3-dichloro-5,6-dicyano-p-benzoquinone inExample 4 so as to obtain four sheets of electrically conductivepolyaniline films having 1-naphthol-4-sulfonic acid novolac resin as adopant. The electric conductivities of these electrically conductivepolyaniline films were measured by Van der Pauw method. The electricconductivities of two sheets of polyaniline films A and B doped for 30minutes were 1.2 S/cm and 2.2 S/cm respectively, while the electricconductivities of two sheets of polyaniline films C and D doped for 1hour were 3.4 S/cm and 4.1 S/cm respectively.

Then, the films A and C were subjected to water resistance test. Theywere immersed in 15 mL of distilled water in a glass sample tube of20-mL capacity for 508 hours and thereafter taken out so as to measurethe electric conductivities thereof. The electric conductivity of thefilm A that had been doped for 30 minutes was 0.78 S/cm, while theelectric conductivity of the film C that had been doped for 1 hour was2.1 S/cm.

The films B and D were subjected to heat resistance test. They werestuck crosswise on a 10 cm-square glass plate with a 2-mm-widepressure-sensitive adhesive tape made of polytetrafluorethylene resin,put into a hot-air circulating type drier at a temperature of 125° C.and then taken out in 508 hours so as to measure the electricconductivities thereof. The electric conductivity of the film B that hadbeen doped for 30 minutes was 0.54 S/cm, while the electric conductivityof the film D that had been doped for 1 hour was 2.8 S/cm.

Thus, it is denoted that the electrically conductive polyaniline film ofthe invention has high water resistance and heat resistance as theelectric conductivity thereof after both the water resistance test andthe heat resistance test had little change as compared with the initialvalue.

1. An electrically conductive polyaniline composition comprising polyaniline doped with naphtholsulfonic acid novolac resins.
 2. An electrically conductive polyaniline composition according to claim 1, wherein the polyaniline comprises a repeating unit represented by the general formula (I)

wherein m and n denote molar fractions of a quinonediimine structural unit and a phenylenediamine structural unit, respectively, in the repeating unit, and satisfy the conditions: 0≦m≦1, 0≦n≦1 and m+n=1.
 3. An electrically conductive polyaniline composition according to claim 1, wherein the naphtholsulfonic acid novolac resin is represented by the general formula (IV)

wherein R₂ and R₃ denote each independently a hydrogen atom, an alkyl group, an alkoxyl group, a hydroxyl group, a carboxyl group or an amino group, and p and q denote each independently an integer of 0, 1 or 2, provided that p and q are not simultaneously
 0. 4. An electrically conductive film comprising an electrically conductive polyaniline composition according to claim
 1. 5. A method of producing an electrically conductive polyaniline composition comprising contacting polyaniline with naphtholsulfonic acid novolac resins to dope the polyaniline with the novolac resin.
 6. A method of producing an electrically conductive polyaniline composition according to claim 5, wherein the polyaniline comprises a repeating unit represented by the general formula (I)

wherein m and n denote molar fractions of a quinonediimine structural unit and a phenylenediamine structural unit respectively in the repeating unit, and satisfy the conditions: 0≦m≦1, 0≦n≦1 and m+n=1.
 7. A method of producing an electrically conductive polyaniline composition according to claim 5, wherein the naphtholsulfonic acid novolac resin is represented by the general formula (IV)

wherein R₂ and R₃ denote each independently a hydrogen atom, an alkyl group, an alkoxyl group, a hydroxyl group, a carboxyl group or an amino group, and p and q denote each independently an integer of 0, 1 or 2, provided that p and q are not simultaneously
 0. 